Agilent Technologies DSO-X 4022A, User Manual

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Acquisition Control
12
Agilent InfiniiVision 4000 X-Series Oscilloscopes User's Guide 217
So, in practice, an oscilloscope's sample rate should be four or more times
its bandwidth: f
S
= 4f
BW
. This way, there is less aliasing, and aliased
frequency components have a greater amount of attenuation.
Note that 1.5 GHz bandwidth 4000 X- Series oscilloscope models have
more of a brick- wall type frequency response than the Gaussian response
of lower bandwidth 4000 X- Series oscilloscope models. To understand the
characteristics of each type of oscilloscope frequency response, see
Understanding Oscilloscope Frequency Response and Its Effect on
Rise- Time Accuracy
, Agilent Application Note 1420
( "http://cp.literature.agilent.com/litweb/pdf/5988- 8008EN.pdf" ).
See Also Evaluating Oscilloscope Sample Rates vs. Sampling Fidelity: How to
Make the Most Accurate Digital Measurements
, Agilent Application Note
1587 ( "http://cp.literature.agilent.com/litweb/pdf/5989- 5732EN.pdf" )
Oscilloscope Rise Time
Closely related to an oscilloscope's bandwidth specification is its rise time
specification. Oscilloscopes with a Gaussian- type frequency response have
an approximate rise time of 0.35/f
BW
based on a 10% to 90% criterion.
Figure 36 Sample Rate and Oscilloscope Bandwidth
Limiting oscilloscope bandwidth (f
BW
) to 1/4 the sample rate (f
S
/4)
reduces frequency components above the Nyquist frequency (f
N
).
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